1. Field of the Invention
The present invention relates to an electric operation apparatus, and more particularly to an electric operation apparatus and an output control method featuring a specific output control section for high frequency current.
2. Description of the Related Art
Electric knives and other types of electric operation apparatus are commonly used to incise or coagulate biological tissue, to stop bleeding, or to perform other procedures when internal or external surgery is conducted.
Such an electric operation apparatus comprises a high frequency cauterizing power supply unit and a treatment means connected to the high frequency cauterizing power supply unit, with the aforementioned treatment being performed by the application of the treatment means to the patient and feeding high frequency power from the high frequency cauterizing power supply unit.
Various proposals have been made concerning the aforementioned electric operation apparatus. For example, Japanese Patent Laid-open No. H8-98845 discloses a technique in which coagulation completion is verified on the basis of tissue impedance, and high frequency output is stopped in order to prevent the coagulating tissue from carbonizing and adhering to electrodes.
A technique for reducing the high frequency output in order to achieve the same object as in Japanese Patent Laid-open No. H8-98845 is also disclosed in connection with the electric operation apparatus described in Japanese Patent Laid-open No. H10-225462.
It should be noted that tissue impedance varies more rapidly with a reduction in the contact area between the tissue and the electrodes.
The electric operation apparatus described in Japanese Patent Laid-open Nos. H8-98845 and H10-225462 are configured such that, in case a narrow contact area is formed between the tissue and the electrodes, the tissue, sometimes, carbonizes or adheres to the electrodes while tissue impedance is measured or coagulation completion is verified.
Japanese Patent Laid-open No. H10-225462 discloses a technique in which the output of a high frequency current is reduced without being stopped after coagulation completion has been verified. According to this technique, a treatment can be continued if a surgeon or other specialist determines that insufficient coagulation has been achieved following verification of coagulation made by an electric operation apparatus. In the process, tissue degeneration can be slowed down due to reduced high frequency output, and the specialist can terminate the treatment once the desired coagulation state has been achieved.
However, the small size of the contact area between the tissue and the electrodes speeds up tissue degeneration and makes it more difficult for a specialist to terminate treatment once the desired coagulation state has been achieved. Another drawback is that a large contact area results in excessively slow tissue degeneration, and takes too long to obtain the desired coagulation state.
Yet another feature is that reducing the contact area between the tissue and the electrodes tends to make impedance, electric current, and the like susceptible to the influence of electrode operation and the like, and allows these parameters to be affected by factors unrelated to the coagulation state of the tissue.
The electric operation apparatus disclosed in Japanese Patent Laid-open Nos. H8-98845 and H10-225462 are disadvantageous in that when a small contact area is formed between the tissue and the electrodes, measurement results concerning electric current and the like become unstable and coagulation is sometimes considered to be complete even though in reality it is not.